The trick is to figure out what the IRS is going to think, and it's not entirely clear from Pub 3079: Tax-Exempt Organizations and Gaming. There is a lot of discretion in these matters, and there's not a good way to know what the IRS will say ahead of time.

My feeling is that it's not worth it. TPF isn't hurting for money, so risking their tax-exempt status (along with generating more work to track and report income) for what's probably going to be not-so-much money probably isn't worth it.

People who want to give money to TPF can just give money to TPF. Even with the auctions, there's no items that are particularly desirable or high-end enough to attract big money.

If you want to play poker informally and give all your winnings to TPF, that's your own business. :)